Performance optimization of perovskite solar cells using p-InGaN as a hole transport layer: A numerical comparison with spiro-OMeTAD and HTL-free designs

Perovskite solar cells (PSCs) commonly utilize organic materials as a hole-transport layer (HTL) to enhance hole extraction to the back electrode, thereby boosting device performance. These organic HTL are chemically and thermally unstable, degrading when exposed to air and moisture. This work, for the first time, attempts to explore the possibility of replacing the conventional organic HTL with the thermally and chemically stable, high hole mobility, inorganic III-nitride p-InGaN material as an HTL in PSC. The p-InGaN HTL-based PSC achieved a power conversion efficiency (PCE) of 21.6%, which is reasonable when compared to the PCE of 32.9% and 34.5% delivered by the conventional organic Spiro-OMeTAD HTL and the HTL-free configurations. These can be attributed to the assisted hole extraction by the HTL and the direct contact of the MAPbI 3 perovskite absorber with the optimal higher work-function Pt back contact for the Spiro-OMeTAD HTL-based and HTL-free-based devices, respectively. We observed that variations in the back metal contact have a significant impact on the PCE of Spiro-OMeTAD HTL-based and HTL-free PSC, respectively. Although the p-InGaN and Spiro-OMeTAD HTL-based PSCs demonstrate equivalent values of PCE at all high temperatures, 400–700 K. The HTL-free cell shows higher thermal resilience compared to its HTL-based counterpart devices. Our work reveals that utilizing the p-InGaN HTL increases longevity due to material stability, whereas eliminating the HTL can deliver higher PCE and reduced costs.